If electrons drift relative to ions across a magnetic field, three types of electrostatic cross-field instability can occur at frequencies much greater than the ion cyclotron frequency. These have been predicted to cause particle heating and perhaps anomalous diffusion. The experiments on each type are described. The main observations include linear and nonlinear wave properties, together with the ion heating associated with the two low frequency modes.
The thermal annealing effects of stacking layers Mo/Si were studied by Rutherford back scattering (RBS), optical reflection, scanning electron microscopy (SEM), X-ray diffraction and X-ray reflection methods. In RBS measurement of Mo/Si system, diffusion phenomena appeared at higher annealing temperature than 400°C. In the other methods, remarkable changes were also observed in respective spectral profiles for the system annealed at the temperature higher than 500°C. The density of Mo metal film was estimated as 80% or more of bulk material.
This study deals with the simultaneous measurements of Doppler and B-mode. The ultrasonic beam for B-mode and that for Doppler are transmitted and received perfectly at the same time. To avoid the crosstalk between two beams, the center frequencies of 2.5 and 3.5MHz are used and bandpass filters are applied. An analysis, the experimental results and the results for a normal human heart are presented.
It has been known that transfer RNA assumes a functional conformation in the presence of certain metal ions, most commonly magnesium ions. Several Mg2+-binding sites of high affinity have been revealed by X-ray crystallographic analyses of yeast tRNAPhe. On the other hand, ATP, a naturally occurring high-energy compound and which is one of the substrates in aminoacylation of tRNA, is known to have ability to chelate Mg2+. We therefore examined the possibility that the conformation of tRNA is regulated by the quantitative balance between Mg2+ and ATP, and consequently biological activity of tRNA is modulated as well. Structural transition of tRNA was monitored by measuring the melting profiles of yeast tRNATyr in the presence of Mg2+ and/or ATP at various [ATP]/[Mg2+] ratios. Tyrosine-accepting activity of yeast tRNATyr was also measured under the similar solution conditions. These results clearly indicated that conformation of tRNA and its aminoacylation capacity can be easily modulated by changing the relative concentration ratio of Mg2+ and ATP.
A variant of Torulopsis utilis tRNAVal containing base substitution (C to U) at the third letter of the anticodon has been prepared by several enzymatic reaction steps in vitro. The valine-accepting activity of this variant, tRNAVal(IAU), was found to be decreased to a great extent. This result suggests that the third letter (C) of the anticodon of yeast tRNAVal is strictly recognized by the Valyl-tRNA synthetase (ValRS). Combinations of 5'-half and 3'-half fragments were used to assess the importance of the anticodon loop conformation on aminoacylation. The result of this experiment indicated that the base-stacking interactions in the 3'-side region of the anticodon loop have a crucial role in the recognition of this tRNA by its cognate ValRS. In summary, both of the nucleotide sequence and the conformation of the anticodon loop are significant elements for T. utilis tRNAVal-ValRS recognition.
Electron beam treatment is one of the most promising surface technologies. The advanced state of beam control allows the treatment even of components of complicated shape in agreement with their contours and service conditions by means of solid state transformations or liquid phase processes. After a brief description of the process technology, the possibilities mainly for remelting and remelt alloying will be illustrated by examples.